This invention relates to dual wheels for vehicles such as trucks and fastening systems for securing these wheels in place.
It is well known that vehicle wheels can be mounted on a wheel hub having threaded studs projecting therefrom by means of a number of wheel nuts. This system can be used to mount not only single wheels, such as those found on automobiles, but also dual wheel assemblies generally used on large vehicles such as trucks. In a dual wheel arrangement having inner and outer metal wheels, each wheel has a wheel disc having a number of round, stud-receiving holes formed therein. Central sections of these discs are normally flat and are shaped so as to rest against one another when the two wheels are secured to a hub.
One known system for attaching both single wheels and dual wheels to a vehicle involves the use of cone lock nuts or two piece flange nuts to clamp the wheel in position. Use of these nuts is said to provide greater clamping force on the wheel (up to 150% greater than ball seat double cap nuts). Users of these nuts also claim that they provide a broader, more positive nut-wheel contact. These nuts comprise two pieces including a hexagonal body with wrenching surfaces formed around its circumferential perimeter and a washer portion rotatable on the nut body and having a conical outer surface. These nuts are generally used with hub-piloted wheel mounting systems. In use these cone nuts should be lubricated with a suitable oil in the area of the contact surfaces between the washer and the nut body.
However, even with the use of these cone nuts, problems are still being encountered with the mounting of truck wheels. These problems can result in a very dangerous situation if the nuts become sufficiently loose and eventually come off, permitting the wheel to come off the vehicle which may be moving at a high rate of speed. A number of attempts have been made to solve this problem but none of these proposed solutions have been entirely successful.
In recent years, hub piloted systems, which use the above described cone nuts, have been developed for mounting truck wheels. In such systems, the wheel hub is provided with hub pilot pads in order to position the wheel assembly or assemblies properly on the wheel hub. The hub-piloted system uses four, or in some cases five or six, pads strategically arranged on the hub to position the wheel horizontally and vertically. Once the wheel is in position, the cone nuts are then used by threading them onto the studs in order to clamp the wheel or wheels in place. Although such systems are more expensive than the alternative ball seat system, they claim to have increased clamping force and fewer, more simply maintained components.
However with hub-piloted systems, there is nothing to prevent the wheel or wheels from undergoing a circular (clocking) movement if there is a loss of torque applied to the side of the wheel by the cone nuts. This torque can be lost for a number of different reasons including contamination of the wheel mounting components by dirt or salt, worn hub pads, worn wheel mounting holes, over torqued nuts, bad installation procedures, and an impact on the wheel mounting caused by strong braking or engine torque.
Early U.S. Pat. No. 2,150,110 issued Mar. 7, 1939 to J. W. Tatter teaches a wheel structure which is mounted upon a hub by means of a number of bolts or studs that are mounted in the hub. Nuts are used to secure the wheel to the bolts and each nut has a normally concavo-convex spring washer swivelled onto an axially projecting flange formed on the nut. The flange has its end portion peened over so as to retain the washer in permanent association with the nut. According to the patent specification, the spring of the washers takes up any looseness of the nuts, thus helping to retain the wheel on the hub.
Much more recent U.S. Pat. No. 4,431,353 issued Feb. 14, 1984 to Russell Burdsall & Ward Corporation, describes a fastener assembly used to mount a vehicle wheel on a hub. This assembly includes a nut which is rotatable relative to a washer to enable the fastener assembly to be tightened without marring the wheel. The washer has an annular collar which is loosely connected with a nut by a retainer section which extends from one axial end portion of the nut. The washer also has an annular load transmitting and indicating section which extends radially outwardly from the collar and this section includes a spring section which flares radially and axially outwardly from the bearing section. When the fastener assembler is tightened with a predetermined preload, the spring section is flattened to provide a visual indication that the desired preload has been applied.
Early U.S. Pat. No. 2,017,114 issued Oct. 15, 1935 to Motorwheel Corporation describes a clamping nut assembly for mounting dual wheels on a vehicle hub. The dual wheels include a pair of side-by-side discs having holes in a central portion for receiving the wheel studs or securing bolts that project from an annular flange formed on the hub. Threaded onto the bolts are clamping nut assemblies each of which includes a tubular or skirt section and a polygonal head formed integrally with the skirt section. The outer surface of the tubular section snugly engages the inner surface of the openings formed in the two discs. Also, a cup-like washer encircles the tubular member and is secured in position against the head of the nut by a resilient ring.
One difficulty with the clamping nut assembly of the aforementioned U.S. patent is that the tubular or skirt portion of the nut is unduly and unnecessarily long, extending through the holes formed in both wheel discs. In addition to increasing the cost of the nut assembly, it can cause problems, including undue difficulty in installing the nut assembly through both holes in the wheel disks (for example, if one of the holes is slightly misaligned with the adjacent hole) and jamming of the nut assembly in the wheel disc holes. Jamming can occur, for example, if some movement should occur between the inner and outer wheel discs during use of the dual wheel assembly on a vehicle.
It is an object of the present invention to provide an easy to use and reliable combination of a dual wheel for a vehicle and means for securing this dual wheel to a vehicle wheel hub.
It is a further object of the present invention to provide a reliable dual wheel system for a vehicle, which system includes inner and outer wheel assemblies comprising inner and outer metal wheels and a number of clamping nuts, each including a washer rotatably mounted thereon. The nuts are provided with cylindrical skirt portions which extend only into the round, stud-receiving hole of the outer wheel. With this dual wheel system, the skirt portion of each nut prevents clocking movement of the wheel clamped by the nuts even if the torque on the wheel nuts is lost.